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FPGA designers using VHDL have three choices: Stick with VHDL, switch to SystemVerilog, or.. use the best of both. This guest blog from Doug Perry, Senior Member Technical Staff at Doulos, outlines the pros and cons of each.

The latest crop of FPGA devices are enormous when compared to ASICs that were built not that long ago. Verifying these ASICs required detailed plans, multiple tools, and sometimes special languages. Verification was key because the cost of a respin was prohibitive. FPGA designers using VHDL have three choices: Stick with VHDL, switch to SystemVerilog, or.. use the best of both. This guest blog from Doug Perry, Senior Member Technical Staff at Doulos, outlines the pros and cons of each.

The same is not necessarily true of FPGAs because they can simply be re-programmed when an error is found. However the cost of finding the error in the lab can still be very expensive. This is related to the fact that the number of LUTs available in the device has skyrocketed, but the number of IO pins has not. Therefore getting visibility into the inner workings of the device from outside becomes much more difficult. Finding the source of an error therefore also becomes increasingly difficult. To counteract this problem, designers need to find errors before the device gets into the lab. To do this they need to adopt ASIC-like verification methodologies.

Here in Europe, I recently had the opportunity to work with Jim Lewis, OS-VVM Chief Architect and IEEE 1076 Working Group Chair, on the first Advanced VHDL Testbenches & Verification training course. This training, held in Bracknell, UK, was attended by engineers from several major European system companies who design and verify programmable devices (FPGAs). VHDL is by far the dominate language used by Europe’s system companies for the design and verification of FPGAs, however it is unclear to many how to enhance their verification with VHDL. What I have found is that experienced FPGA design engineers (including myself) are not utilising the VHDL language for verification.

Jim Lewis introduces VHDL’s verification capabilities, including new VHDL 2008 features and the Open Source VHDL Verification Methodology (OSVVM). OSVVM provides a methodology for testbench development and verification packages that provide functional coverage and random value generation.(more…)

Here at the Aldec corporate office, we have a sign that reminds us all of our mission in the field of Technology. It reads, ‘To deliver solutions that provide the highest productivity to value ratio; supporting our existing products while delivering innovation to current and new technologies’. We have similar statements to reaffirm our commitment in the areas of Research, Alliances, and Culture – we call it our “Aldec DNA”.

Because we genuinely want to have a clear understanding of our user’s requirements and methodology preferences, we continually engage in surveys and interviews. The knowledge we gain better positions us to support our existing products and to deliver that support where it matters the most to our users. If you’ve ever had that frustrating experience where your favorite tool no longer supports your methodology of choice – then you understand why this is so important.

Our Commitment to the VHDL Community

When it comes to VHDL-2008, we have learned from our customers that many are happy using the methodology – and continue to successfully deliver cutting-edge technology with it. So, while we remain committed to delivering innovation to new technologies, our R&D teams also invest a great deal of development time to ensure that Aldec solutions continue to offer a high level of support for popular languages like VHDL.

Jim Lewis, VHDL Training Expert at SynthWorks (and founding member of OSVVM, which Aldec was an early adopter of) was kind enough to author a guest blog for Aldec. Here’s an excerpt:

After presenting a conference paper on how to do OSVVM-style constrained random and intelligent coverage (randomization based on functional coverage holes), I received a great question, “Why Randomize?”

The easiest way to answer this is with an example. Let’s look at a FIFO test – test a FIFO, write to it, read from it, write to it and read from it simultaneously, fill it and see that additional writes are held off successfully, and empty it and see that additional reads are held off successfully.

Most certainly a FIFO can be tested using a directed test (just code, no randomization). The following simulation waveform shows diffcount (the number of words in the FIFO) for a directed test. The lowest value is empty. The highest is full. Using this, you can visually check off all of the required conditions and see that the FIFO is indeed tested.

As the proud Product Manager of Aldec’s FPGA Design Simulation solution, I am excited (like it was my first Cranberries concert) to announce that Active-HDL™ is celebrating 16 years since its initial release in 1997. Active-HDL has not merely stood the test of time, it has dominated the FPGA market like a Hulk Hogan smackdown with powerful simulation performance and debugging tools.

The key to Active-HDL’s long-term success lies in Aldec’s customer-centric philosophy. Simply put, we really do listen closely to our users and invest heavily in our tools. For this reason, continued simulation performance optimizations from release to release enable users to benefit from Active-HDL’s faster simulation even as the size of FPGA designs continues to grow.

The ability to adopt methodologies and get up to speed quickly is critical in today’s fast moving environment. Aldec offers Fast Track™ ONLINE trainings designed for busy engineers to increase their productivity and enhance their skill level from the comfort of their own browser.

Got SystemVerilog? While it may be a fashionable topic among verification engineers, it’s generally a shunned subject among hardware designers. While there are many good reasons for this (overgrown size of the SystemVerilog standard, expensive options required to use many language features in simulation, poor support in low-end tools, etc.), designers familiar with classical Verilog can benefit greatly from the features available in the Design Subset of SystemVerilog. Designing state machines is one excellent example. It is as easy and elegant in SystemVerilog as it is in VHDL – and those machines even synthesize in better tools!

Digital design has come a long way since its inception from drawing schematic on paper, to CAD tools which can be used to draw schematics, and to today’s most popular (and efficient) process of describing designs through HDLs.

I recently encountered a customer with a legacy design developed in block diagram format. If he hadn’t been an Aldec customer, he might have been stuck. Fortunately, Aldec Active-HDL™ provides utilities for importing legacy schematic based designs from Xilinx® Foundation Series, ViewLogic™, ViewDraw™, Active-CAD™ or any schematic tools that can output an EDIF netlist.

Productivity Boosting Features
Yes I did, but with no intention to start a holy war on which HDL editor is best. When it comes to HDL editors, each engineer has their own choice and I am not attempting to hurt any madly, deeply felt sentiments. My goal is only to bring the awareness to those using the HDL editor built into Active-HDL™ and to help them use it more efficiently.

There are two main categories for HDL editors (1) general purpose text editors, and (2) integrated text editors. Both have their own pros and cons, and in the end it is for each engineer to decide which suits their needs.

The HDL editor built into Active-HDL falls under the second category of integrated text editors. It offers many basic features (syntax highlighting, templates, columns selection, code folding, auto-formatting) as well as semantic features (code navigation, on-the-fly error detector), and also offers seamless integration with the simulator and version control system. The HDL editor in Active-HDL can be used with VHDL, Verilog, SystemVerilog, SystemC, C/C++, PSL, OVA, Perl scripts and Tcl scripts.